Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$179.83	4.190%	$187.3649	$187.36	$187.35	$187.40
Purchase #2	$176.28	10.555%	$194.8864	$194.89	$194.90	$194.90
Purchase #3	$162.64	3.137%	$167.742	$167.74	$167.75	$167.70
Purchase #4	$50.44	13.337%	$57.1672	$57.17	$57.15	$57.20
Purchase #5	$147.39	10.534%	$162.9161	$162.92	$162.90	$162.90
Purchase #6	$55.59	7.400%	$59.7037	$59.70	$59.70	$59.70
Purchase #7	$22.77	13.654%	$25.879	$25.88	$25.90	$25.90
7 purchase totals =	$794.94		$855.6593	$855.66	$855.65	$855.70